No hate comms, but I am not a huge two stroke guy as you may all know. This doesn’t mean I don’t like riding them when I do but if someone gave me an F, Marry, Kill to play and the 125 was one of the three choices, I most likely will be killing the 125. Sorry, peace and love. I get to test all kinds of two strokes but I can genuinely say that 125s are usually the most fun for me in the two stroke realm.
Come 2025, I had a chance to test the YZ125 but this time for a prolonged period of time. The 2025 YZ125 hasn’t changed from 2022 with the exceptions of bold new graphics. The bLU cRU YZ125 is listed for $7,099 and to me is still a great buy for some fun and we will explain why below.
The YZ initially got its major over hall in 2005 with the aluminum frame and in 2006 with KYB SSS suspension upgrade. Between 2006 and 2021 their where minor changes here and there in attempts to keep the bike progressing. The motor had always been a good off the bottom 125 compared to its competition and that along with its excellent handling manners is what always kept the bike relevant. In 2022 the motor got a complete redo to provide a more mid and top end performance motor. The bottom end still maintained good power but it was a little less error friendly than the previous generation motor. The hope was to align the new motor to better compete with the competition. The chassis and suspension have always been the YZ125 sweet spot and the 2025 generation bike continues to hold down that position. Any day railing around the track on a YZ125 is a blast and will bring a huge smile to anyone who swings a leg over the bike.
I’m a vet rider at 5’11, 175 pounds on a good day and my bike of choice is a 450F. I am not the classic 125 demographics, neither age nor size, but more and more vet moto guys are enjoying the close racing found on small bore bikes that don’t penalize you with every mistake. The suspension on the YZ125 is ideally set for 140-165 pounds but despite my size the suspension is still capable for a fairly aggressive rider on the track. The SSS forks and KYB shock are very predictable and manage big hits without any harsh transition to the rider. The SSS forks are consistent with performance throughout the day and provide a front end that feels planted on both flat and off camber turns. I tend to run my suspension fairly soft but for those riders above 175 pounds, realistically stiffer springs will be required. The rear shock is also under sprung for myself but still performed well on big hits, heavy braking bumps and acceleration bumps in the ruts. Optimal sag for the YZ125 is 100-102mm but due to this rider size, I ran sag at 105mm as I wanted to keep the static sag in an acceptable range without too much preload.
The handling of the YZ125 chassis has been a class leader for years and the 2025 YZ125 remains second to none. The chassis has a supple feeling without any harshness or sense of deflecting. The chassis and suspension felt planted and comfortable on lean angle as well as setting up for corners, the bike wants to stay in the rut mid corner and exits and finishes corners very well. The rear end even though under sprung for this rider, didn’t seem to squat and disrupt mid corner and exit corner performance to any appreciable extent. I did notice some slight repeated head shake with fast, heavy braking bumps which I assumed was due to the fork being under sprung and low in the stroke in the front end. Outside of that, the handling, performance and fun factor of this bike is awesome.
The motor on the YZ125 was all new in 2022 and remains the same for 2025. The motor has a solid bottom end with strong mid-range and top end performance. Is this motor better than the previous 2021 motor? Depends on who is riding it. For the faster more experienced rider, the “updated” engine will produce faster lap times. The 2021 YZ125 motor was more bottom end oriented with a good transition to mid power but didn’t have the top end needed to be a class leader in horsepower performance. In a class all about horse power the pre 2022 Yamahas hung tough with their handling prowess but struggled against the Austrian 125s when it came to all out-motor performance in stock form. The 2025 YZ125 has a good low end rpm response but can be a little rich feeling under 6000 rpm if you’re lugging it a bit, which I was doing A LOT when I first got on this sucker. My mind took a bit to downshift two times into a corner versus one time so I got to know the jetting a little bit more because of this. I prefer the GYTR jetting kit (when in stock, is the best jetting) as it leans the bike out a little down low and gives the rider more low end feel out of corners. Mid to top end the jetting seems good and doesn’t detonate or seem rich and I really like the clean feel this blue 125 puts out over a KTM personally.
By the 10 hour testing mark I decided it was time to try some easy bolt on modifications. Easiest and least expensive modification was to add an additional tooth to the rear sprocket to assist the YZ125 in loamy conditions. The stock motor with the new Renthal 13/50 sprocket (stock 13/49) was a definite improvement in bike performance. The ability to not have to abuse the clutch and in general pull harder in deeper soil and bigger hills was immediately felt. I was now able to get into third gear more in corners and the bike responded more effectively to clutch slipping. For riders north of optimal 125 weight this is an inexpensive improvement with nice performance gain.
At the end of the day and this is tough for me to say, the YZ125 brings a lot of fun to my riding. Son of a bitch! It almost relaxes me and I don’t feel like I have to go fast because the 125 is simply not that fast. I get into a different mind set when I ride the 2025 YZ125. So, what I am saying, it’s fun, go buy one if you want a 125. Damn it!
Suggested Suspension Settings:
Fork:
Spring rate: 4.2 N/m (North of 170 pounds you will need 4.4-4.6 N/m springs)
Compression: 8 clicks out
Rebound: 10 clicks out
Fork height: 3mm up
Shock:
Spring rate: 48 N/m
Race sag: 102mm
Hi Speed Compression: 1-1/4 turns out
Lo Speed Compression: 11 clicks out
Rebound: 11 clicks out
We also got a jetting spec that we liked. The stock jetting is a little rich (nothing horrible) as we got a little rich feeling at times off faces of jumps so we decided to try a different jetting spec and just altered it a little for sea level to 4000 feet. We have used a stock pipe/silencer as well as a PC set up with this jetting with good results. We tested with pump gas and it was a little rich so going to a 165 main with pump gas helps. With VP T2 or C12 this jetting below was the best. The key to this jetting spec is the Y4 needle that you can get from Pro Circuit or the GYTR kit. They sell out quick, so get them ASAP!
Recommended Jetting:
168 main
62 Pilot
Y4 needle in the 2nd clip position
1 to 1.25 turn out on fuel screw
